GPG keys for Ubuntu package signature verification

https://bugs.launchpad.net/ubuntu/+filebug

Universal charset detection library

https://www.freedesktop.org/wiki/Software/uchardet/

Data compression library with low memory usage

https://www.oberhumer.com/opensource/ucl/

Command-line tools for building TCP client-server applications

http://cr.yp.to/ucspi-tcp.html

DNS resolver library with sync and async queries

https://www.corpit.ru/mjt/udns.html

Fast copy utility for UFS filesystem

http://people.freebsd.org/~simokawa/ufs/

HTTP web service mocking library for GNOME

https://gitlab.com/groups/uhttpmock

Convert MagicISO UIF files to ISO9660

http://aluigi.altervista.org/mytoolz.htm

Ultra lightweight xml-rpc library written in C++

http://ulxmlrpcpp.sourceforge.net/

Extract, view & test ACE archives

http://www.winace.com/

Allows files to be extracted from ARJ archives

http://www.arjsoftware.com/

Validating, recursive, and caching DNS resolver

https://www.nlnetlabs.nl/projects/unbound

Remove idle cursor image from screen

Unicode emoji data files

http://www.unicode.org/emoji

Library for single instance applications

https://wiki.gnome.org/Attic/LibUnique

Fork of Exuberant Ctags to generate index/tag files

https://ctags.io/

Local self-authentication for pam_exec

https://github.com/Zirias/unix-selfauth-helper

Convert ASCII newlines between CR/LF and LF

ODBC library suite for Unix

http://www.unixodbc.org/

BYTE magazine's Public Domain benchmark for UNIX

https://github.com/kdlucas/byte-unixbench

Extract Makeself archives

Convert any document from and to any LibreOffice supported format

http://dag.wieers.com/home-made/unoconv/

Extract, view & test RAR archives

https://www.rarlab.com/

Lists/Extracts files from a "*.tgz" or "*.gz" archive

List, test, and extract compressed files from a ZIP archive

http://infozip.sourceforge.net/UnZip.html

Zoo archive extractor

http://freshmeat.sourceforge.net/projects/unzoo/

Universal Plug and Play Software Development Kit

http://pupnp.sourceforge.net/

D-Bus daemon for simplifying power management tasks

http://upower.freedesktop.org/

Ultimate Packer for eXecutables

https://upx.github.io/

URI parsing library

https://github.com/uriparser/uriparser

URL extractor/launcher

https://github.com/sigpipe/urlview

Another font package for X

Unicode TrueType fonts from URW extended by Valek Filippov

Database of all known IDs used in USB devices

http://www.linux-usb.org/

Daemon for multiplexing connections over USB to iPhone/iPod Touch

http://www.libimobiledevice.org

Simple, portable, lightweight library for handling UTF-8 strings

http://utfcpp.sourceforge.net/

UTF-8 processing library

https://juliastrings.github.io/utf8proc/

hash table for C structures

http://uthash.sourceforge.net/

Library for uu/xx/Base64/BinHex/yEnc de-/encoding

http://www.fpx.de/fp/Software/UUDeview/

Monospaced bitmap fonts for X11

https://people.mpi-inf.mpg.de/~uwe/misc/uw-ttyp0/

Video4Linux utilities

https://linuxtv.org/wiki/index.php/V4l-utils

Video4Linux IOCTL header files

https://linuxtv.org

Implementation of the UNIX 7th Edition shell

http://minnie.tuhs.org/UnixTree/V7/

Programming language and compiler that converts Vala code into C code

https://wiki.gnome.org/Projects/Vala

Memory debugging and profiling tool

https://github.com/paulfloyd/freebsd_valgrind

Markup Validation Service from the World Wide Web Consortium (W3C)

http://validator.w3.org/

Vamp audio analysis plugin SDK

https://www.vamp-plugins.org/

Video processing framework with simplicity in mind

https://www.vapoursynth.com/

High-performance HTTP accelerator

http://www.varnish-cache.org/

High-performance HTTP accelerator

http://www.varnish-cache.org/